Are you viewing the video output directly from the console HDMI port? If you just use Chiaki to send controller data, and not view its video output, you can eliminate that part of the round trip time. Set the resolution to the lowest possible setting if you aren't viewing it.
Use a wired network between the PC and the console.
Check the PC's task manager process list, and sort by CPU % and look for anything you don't need running that might be consuming resources.
Since we went found the Remote Play PS5 solutions, several USB adapters have become available. It might be time to switch over.